ID: SPDisposeCheckID_140
Module: xx.xx.dll
Method: xx.xx.Layouts.xx.UpdateWorkspace.Page_Load(System.Object,System.EventArgs)
Statement: RootWeb := RootSite.{Microsoft.SharePoint.SPSite}get_RootWeb()
Source: UpdateWorkspace.aspx.cs
Line: 201
Notes: Disposable type not disposed: Microsoft.SharePoint.SPWeb
***This may be a false positive depending on how the type was created or if it is disposed outside the current scope

It would seem that the tool is suggesting that you should dispose the RootWeb instance obtained from RootSite.RootWeb.
If that is the case, you shouldn't worry, as RootWeb no longer requires explicit dispose - disposing will be automagically get taken care of by the parent SPSite object. There is even a specific guidance on the same blog:

An earlier version of this article indicated that the calling
application should dispose of the SPSite.RootWeb property just before
disposing of the SPSite object that is using it. This is no longer the
official guidance. The dispose cleanup is handled automatically by the
SharePoint framework. Additionally, SPSite properties LockIssue,
Owner, and SecondaryContact used the RootWeb property internally.
Given the updated guidance for RootWeb, it is no longer advisable to
call the Dispose method on the SPSite.RootWeb property whenever any of
these properties are used.

This best practice addresses the issue identified by the SharePoint
Dispose Checker Tool as SPDisposeCheckID_140.